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Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Quality Management COMP 3663 Daniel L. Silver.

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Presentation on theme: "Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Quality Management COMP 3663 Daniel L. Silver."— Presentation transcript:

1 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Quality Management COMP 3663 Daniel L. Silver

2 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Quality Management l Managing the quality of the software process and products l Also known as … Quality Assurance (QA)

3 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Objectives l To introduce the quality management process and key quality management activities l To explain the role of standards in quality management l To explain the relationship between quality attributes and software metrics l To explain how measurement may be used in assessing software quality

4 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Software quality management l Concerned with ensuring that the required level of quality is achieved in a software product l Involves defining appropriate quality standards and procedures and ensuring that these are followed l Should aim to develop a ‘quality culture’ where quality is seen as everyone’s responsibility

5 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches What is quality? l Quality simplistically, means that a product should meet its specification l This is problematical for software systems Tension between customer quality requirements (efficiency, reliability, etc.) and developer quality requirements (maintainability, reusability, etc.) Some quality requirements are difficult to specify in an unambiguous way Software specifications are usually incomplete and often inconsistent

6 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Software quality attributes

7 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches A high quality software product … l Satisfies clearly stated requirements l Reacts in predictable ways to illegal inputs l Has been inspected thoroughly l Has been tested exhaustively l Is been sufficiently documented l Has a known defect rate

8 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches The quality compromise l We cannot wait for specifications to improve before paying attention to quality management l Must put procedures into place to improve quality in spite of imperfect specifications l Quality management is therefore not just concerned with reducing s/w defects but also with other product qualities l True/False? … The quality of the process affects the quality of the product.

9 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches l The quality of a developed product is influenced by the quality of the production process l Form (product) follows function (process) l Particularly important in software development as some product quality attributes are hard to assess l Complex and poorly understood relationship between software processes and product quality Process and product quality

10 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Process-based quality l Straightforward link between process and product in manufactured goods l More complex for software because: The application of individual skills and experience is particularly imporant in software development External factors such as the novelty of an application or the need for an accelerated development schedule may impair product quality l Care must be taken not to impose inappropriate process standards

11 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Process-based quality

12 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Quality in the Software Process l Quality principles – overarching quality guidelines l Quality planning – quality plan defines approach to quality l Inspections – peer processes focused on quality l Reviews and Audits – external quality assessment l Defect management – ID, tracking, resolution of defects l Process improvement – continuous upgrading of processes l Organizational quality – engineering competence levels

13 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Quality Principles l Focus continuously on quality l A quality assurance process must be defined l The organization must follow its quality assurance process l Find and repair defects as early in the development process as possible

14 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches 3. Plan4. Design and build 5. Deliver & main- tain the product 1. Specify how to manage project documents 2. Identify process QA 1. QA Develops and/or reviews configuration management plans, standards QA develops and/or reviews provision for QA activities 2. QA reviews process for conformance to organizational policy 5. QA reviews, inspects & tests 4. QA reviews, inspects & tests Adapted from Software Engineering: An Object-Oriented Perspective by Eric J. Braude (Wiley 2001), with permission. Quality Planning Quality Control QM should have some independence from PM

15 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches l Standards are the key to effective quality management l Product standards define characteristics that all components should exhibit e.g. a common programming style l Process standards define how the software process should be enacted Quality assurance and standards

16 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches l Encapsulation of best practice- avoids repetition of past mistakes l Education of new staff to expectations of quality l Framework for the quality assurance process Importance of standards

17 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches ISO 9000 l International set of standards for quality management International set of standards l Applicable to a range of organisations from manufacturing to service industries l ISO 9001 applicable to organisations which design, develop and maintain products l ISO 9001 is a generic model of the quality process that must be instantiated for each organisation

18 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches ISO 9000 and quality management

19 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Problems with standards l Not seen as relevant and current by developers l Involve too much bureaucratic form filling l Unsupported by software tools so tedious manual work is involved to maintain standards l What would you suggest to overcome this problem? …

20 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches l Involve practitioners in development. Engineers should understand the rationale underlying a standard l Review standards and their usage regularly. Standards can quickly become outdated and this reduces their credibility amongst practitioners l Detailed standards should have associated tool support. Excessive clerical work is the most significant complaint against standards Overcoming the Problems

21 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Agile - Overcoming the Problems l Focus continuously on quality Close customer contact, BDD, TDD, Paired-Programming l A quality assurance process must be defined Less documentation, more rigour in development / testing l The organization must follow its quality assurance process Report problems at Scrum meetings, ensure solutions l Find and repair defects as early in the development process as possible A natural for Agile methdds

22 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Quality planning l A quality plan sets out the desired product qualities and how these are assessed ande define the most significant quality attributes l It should define the quality assessment process l It should set out which organisational standards should be applied and, if necessary, define new standards

23 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches IEEE Quality Documents Requirements Analysis Design Implementation Project Management V&V Plan 1012 QA Plan 730 Explains verification and validation procedures. Explains plans, procedures, and test cases. Testing 829 Explains quality policies 23

24 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches IEEE Quality Assurance Plan 24

25 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches IEEE Quality Assurance Plan (cont.) 25

26 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches V&V Quality control l Checking the software development process to ensure that procedures and standards are being followed l Two approaches to quality control Quality reviews – inspections Assessment via software metrics - testing

27 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Workshop - A Quality Challenge l Using 5 Cards and 2 pieces of tape construct a platform which can withstand the repeated drop (3 times) of a pack of post-it notes from 1 inch l The end product must: Be at least one card high (either width or height of card) Not have any folded cards (not a wrinkle) Make efficient use of resources (minimize where possible) Be portable (can be moved to a different platform{:]) l The end product should be of high quality: Adaptable (standup to minor changes in requirements) Extensible (capable of enhancement) Reusable (applicable to different situations)

28 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Team Work (3-4 people) l Quality assurance person / tester l Requirements analyst / Designer l Developer

29 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Quality attributes and software metrics l Software measurement is concerned with deriving a numeric value for an attribute of a software product or process l Software metric is any type of measurement which relates to a software system, process or related documentation l This allows for objective comparisons between techniques and processes l There are few standards, no systematic use

30 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Quality attributes and software metrics

31 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches l A software property can be measured l A relationship exists between what we can measure and a quality attribute l This relationship has been formalized and validated Important software metric assumptions

32 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches The measurement process l A software measurement process may be part of a quality control process l Data collected during this process should be maintained as an organisational resource l Once a measurement database has been established, comparisons across projects become possible

33 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches l A quality metric should be a predictor of product quality l Classes of product metric Dynamic metrics which are collected by measurements made of a program in execution Static metrics which are collected by measurements made of the system representations Product metrics

34 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Dynamic and static metrics l Dynamic metrics are closely related to software quality attributes Collected by a program in execution (response time, number of failures) Help assess efficiency, effectiveness, availability and reliability l Static metrics have an indirect relationship with quality attributes Collected from system representation (lines of code) Help assess complexity, understandability and maintainability

35 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Software product metrics

36 Portions from (1) Ian Sommerville - Software Engineering, (2) Eric Braude, SE Modern Approaches Object-oriented metrics


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